JPS61108708A - Electrically conductive porous hollow fiber of regenerated cellulose and its production - Google Patents

Abstract

PURPOSE:The titled hollow fiber where average pore diameters on inner and outer wall surfaces and the porosity on the outer wall surface range in specific range, further copper sulfide or metallic copper disperses in fine particles, thus showing good mechanical properties and filtration performance. CONSTITUTION:The hollow fiber has pores passing through from the outer wall surface to the inner wall surface, average pore diameters ranging 0.02-1mum on the outer and inner wall surfaces, respectively and a porosity of more than 5% on the outer wall surface. In order to make the fiber electrically conductive, a fine particle powder of copper sulfide or metallic copper is dispersed so that more amounts of the powder distribute near the pores. A high electroconductivity is obtained by use of a relatively small amount of the copper powder. USE:Gas diffusion electrodes, filter for electrically charged particles.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention is a porous regenerated cellulose hollow fiber having a novel structure and conductivity, and having an average pore diameter of an inner wall surface and an outer wall surface. The present invention relates to a conductive porous regenerated cellulose hollow fiber having pores in the range of 0.02 to 1 μm, and a method for producing the same.

In addition, in this specification, "porous hollow fiber" means 0.02 in the entire wall thickness part when the wall part is observed with an electron microscope.
Refers to hollow fibers with a structure in which pores of μm or larger are observed.
A hollow fiber in which no such pores are observed is defined as a non-porous hollow fiber.

(b) Prior Art Conventionally, conductive porous membranes have been mainly obtained by sintering metal powder. However, the porous membrane obtained by this method is heavy, has poor workability, is difficult to thin, and has drawbacks such as difficulty in adjusting porosity and average pore diameter. On the other hand, various methods are known for manufacturing porous polymer membranes, such as elution method, wet casting method, and foaming agent method, and it is possible to manufacture conductive porous membranes without the above-mentioned drawbacks. . However, in the past, it was considered impossible to obtain porous hollow fibers directly from a cellulose steel ammonia solution as in the present invention, and furthermore, there was no one in which conductivity was imparted to such hollow fibers.

(c) Problems to be Solved by the Invention The present inventors have conducted intensive research to obtain porous regenerated cellulose hollow fibers with excellent conductivity and various properties from a cellulose steel ammonia solution, and as a result, have arrived at the present invention. Ta.

That is, an object of the present invention is to provide a conductive porous regenerated cellulose hollow fiber that overcomes the above-mentioned drawbacks, has excellent mechanical properties and performance, and can be produced industrially advantageously, and a method for producing the same. .

B) Means for solving the problem The conductive porous regenerated cellulose hollow fiber according to the present invention is a hollow fiber composed of cellulose molecules, and the average pore diameter of the inner wall surface and outer wall surface of the hollow fiber is 0.02. It has reeds within the range of ~1 μm, and the in-plane porosity of the outer wall surface is 5% or more, there are holes that penetrate the inner and outer wall surfaces, and there is a trace of copper sulfide or metallic copper throughout the hollow fiber. It is characterized by being dispersed.

In addition, in the method for producing conductive porous regenerated cellulose hollow fibers according to the present invention, in the steps of extruding a spinning dope consisting of cellulose steel ammonia solution through an annular spinning spout, coagulating, regenerating, washing with water, and winding, The spinning dope is discharged from the spinning nozzle, and a liquid exhibiting coagulability for the spinning dope is discharged from the central spinning nozzle, and the discharged fibrous material undergoes microphase separation before coagulation, and after coagulation, Characterized by sulfurization or reduction treatment.

The conductive porous regenerated cellulose hollow fiber of the present invention is characterized by an average pore diameter of 0.02 to 1 on both the outer and inner wall surfaces of the hollow fiber.
The hollow fibers have pores of μm size, the in-plane porosity of the outer wall surface is 5 μm or more, and the hollow fibers are electrically conductive.

Regenerated cellulose porous planar membranes and porous regenerated cellulose hollow fibers with electrical conductivity are not known. The average pore diameter of known regenerated cellulose conductive planar membranes is approximately 0.01 μm or less), the in-plane porosity of the outer wall surface is also less than 5 cm, and it is non-porous. Compared to the regenerated cellulose hollow fiber of the present invention, the filtration rate is 1/10 or less, which is very low.

The conductive porous regenerated cellulose hollow fibers of the present invention are made from a copper anthonia solution in which copper and the hydroxyl groups of cellulose are chemically bonded on a molecular order.
The dispersion state is extremely uniform and stable over time, and therefore exhibits excellent electrical conductivity that is stable over a long period of time. Further, since copper sulfide and metallic copper are finely dispersed in large quantities near the pores of the hollow fiber membrane, excellent conductivity is exhibited even when a relatively small amount of copper sulfide or metallic copper is used. Here, "copper sulfide" means cuprous sulfide and cupric sulfide, and also includes mixtures of both. Further, a portion of a nickel compound or the like may be mixed. "
The term "metallic copper" refers to a reduced copper compound, in which cuprous oxide and cupric oxide may be partially mixed, and it means that the weight fraction of metallic copper is substantially 70% or more. Generally, the amount of copper sulfide or metallic copper is 5% by weight or more and less than 50% by weight based on the cellulose. If it is less than 5% by weight, almost no conductivity will be observed, and if it is more than 50% by weight, the permeability of the hollow fiber substance will decrease significantly. It is preferably 10 to 30% by weight.

Regarding the method for producing the conductive porous regenerated cellulose hollow fibers of the present invention, a liquid (hereinafter referred to as "hollow agent") to be discharged from the central spinning port is preferably further used as a coagulation bath (hereinafter referred to as "rH solid agent"). ), since a coagulating liquid is used for the spinning dope, the average pore diameter is 0.02
It is possible to obtain reeds within the range of ~1 μm and an in-plane porosity of 5% or more on the outer wall surface. That is, the greatest feature of the method of the present invention is that a coagulating liquid that causes microphase separation in the cellulose copper anthonia solution is used as the hollowing agent (preferably both the coagulating agent and the hollowing agent). .

Here, "microphase separation" means a state in which a concentrated phase or a dilute phase of cellulose is dispersed and stabilized as particles with a diameter of 0.01 μm to several μm in a solution. Also,
The occurrence of microphase separation is confirmed by direct visual observation of the devitrification phenomenon of the yarn during spinning, or by electron microscopic observation of the yarn after spinning by the presence of particles with a diameter of 1 μm or less and 0.02 μm or more.

By employing a coagulating liquid that causes microphase separation in the cellulose steel ammonia solution as a coagulating agent and hollowing agent, solidification also progresses from the outer wall and inner wall (hollow part), and as a result, the inner wall and It becomes possible to increase the average pore diameter of the outer wall portion and increase the in-plane porosity. That is, the pore structure of the inner wall is determined by the composition of the hollow agent, and the pore structure of the outer wall is determined by the composition of the coagulant with which the outer wall comes into contact. The hollow fibers of the present invention can only be produced by a suitable combination of the compositions of hollow agent and coagulant.

As a desirable implementation state of the method of the present invention, the hollowing agent and the coagulant have no hydroxyl group, have a solubility in a 28% by weight ammonia aqueous solution of 10% by weight or more, and contain at least one organic solvent that swells cellulose. There is a method using a mixed solution that contains ammonia and has a composition that causes microphase separation in the cellulose steel ammonia solution. By using a mixed solution containing an organic solvent as a hollowing agent and a coagulating agent, the normally formed skin layer disappears, and pores with an average pore diameter of 0.02 μm or more are formed on both the outer and inner wall surfaces of the hollow fiber. A preferred mixed solution containing an organic solvent is composed of an organic solvent/ammonia/water system, in which the concentration of ammonia relative to water is 5% by weight or less, preferably 3% by weight or less, and the concentration of the organic solvent relative to water is 20 weight tes or more, 160% by weight or less, preferably 35% by weight or more and 110% by weight or less. By using such a mixed solution, the pore size becomes larger, the number of pores per unit hollow fiber membrane area (pore density) increases, and the proportion of through holes increases, making it possible to produce reproducibly and stably. . The term "organic solvent that does not swell cellulose" as used herein means an organic solvent whose degree of swelling is within the range of +51 to -3 when hollow fibers are immersed in the organic solvent at 20°C for 10 minutes.

Examples of organic solvents that can be used in the method of the present invention include ketones such as acetone and methyl ethyl ketone, and amines such as trimethylamine.

The above-mentioned advantages of the method of the present invention can be more easily obtained by using a spinning dope in which the cellulose steel ammonia solution has a cellulose concentration of 4% by weight or more and 10% by weight or less. When the cellulose concentration in the spinning stock solution becomes 4% by weight, the viscosity of the stock solution decreases) and the spinnability of the spinning stock solution deteriorates, resulting in unstable spinning conditions and good reproducibility. It is difficult to obtain thread. If it exceeds 10% by weight, the hollow fibers become hard IP and transparent, and the average pore diameter and porosity decrease, as well as the pore density. The cuprammonium solution used in the method of the present invention is a solution whose main components are copper and ammonia, and is a dark blue solution called Schie &Peitzer's reagent, which is a solvent system that can substantially dissolve cellulose. means.

This solution also contains a portion of cations other than the copper plate or solvents other than ammonia. Furthermore, "cellulose concentration 11" means the weight concentration of cellulose in a cupric ammonia solution.

Compounds for sulfidation or reduction treatment in the method of the present invention include sodium hydrogen sulfite, sodium thiosulfate, sodium sulfite, sodium pyrosulfite, hydrogen sulfide, sodium sulfide, sodium borate hydride, hypophosphite, etc. Can be used. Further, as a solvent during the treatment, water, methanol, ethanol, glycerin, acetone, etc., and a mixed solvent thereof are used.

The conductive porous regenerated cellulose hollow fibers according to the present invention are expected to be used in gas diffusion electrodes, other electrodes, charged particle separation filters, and the like.

Prior to Examples, methods for measuring various physical property values used in the detailed description of the invention are shown below.

Average pore radius, in-plane porosity, pore density> Porous membrane 1tyr1! If the hole radius of an) is r=, and the number of holes existing at r+d is expressed as N (r) dr, then (N(r
) is the pore size distribution function), the first-order average pore radius rl, the in-plane porosity Pr, and the pore density N are the following (1), (2), and (3).
) is given by the formula.

Pr([=π1r N(r)dr (2)N= 1
N(r)dr (3) The moisture inside the hollow fibers, which are in a wet state, is replaced with acetone,
Thereafter, an electron micrograph of the inner and outer wall surface of the hollow fiber obtained by air drying is taken using a scanning electron microscope. A pore size distribution function N(r) is calculated from the photograph by a known method and substituted into equation (1). That is, the photograph of the part for which the pore size distribution is to be determined is resized to an appropriate size, for example, 20 cln x 20.
c++s) and draw 20 test lines (straight lines) at equal intervals on the resulting photograph. Each straight line is
Cross many holes. Measure the length of the straight line that exists within the hole when it crosses the hole, and find this frequency distribution function. If it is difficult to determine whether the hole is on the outer wall (inner wall) of the hollow fiber, consider that all holes observed on the photograph are holes on the outer wall (inner wall) of the hollow fiber. 3) 14 of N calculated by formula is defined as the pore density in the present invention. Also,
The in-plane vacancy in this case is defined as the in-plane vacancy group being twice as much as Pr calculated by equation (2). Using this frequency distribution function, N(r) is determined, for example, by the method of stereology (for example, ``Quantitative Morphology 1'' by Norio Suwa, published by Iwanami Shoten).

Note that the average pore diameter in the present invention is 2F3.

<Surface resistance> Conductive paste was applied to the surface of the dried hollow fiber in a width of 2 m.
The paste is attached at z intervals, a terminal for measuring electrical resistance is brought into contact with the paste, and the resistance value at that time is read.

(e) Functions and Effects of the Invention The conductive porous regenerated cellulose hollow fibers of the present invention have excellent filtration performance, with a 70% filtration rate that is 10 times or more that of known regenerated cellulose conductive planar membranes.

The conductive porous regenerated cellulose hollow fibers of the present invention are produced from a cupric ammonia solution in which copper and cellulose hydroxyl groups are chemically bonded on a molecular order.
The dispersion state is extremely uniform and stable over time, and therefore exhibits excellent electrical conductivity that is stable over a long period of time. Further, since copper sulfide and metallic copper are finely dispersed in large amounts near the pores of the hollow fiber membrane, excellent conductivity is exhibited even with a relatively small amount of copper sulfide or metallic copper.

In addition, when producing conductive porous regenerated cellulose hollow fibers, by using a coagulating liquid that causes microphase separation in the cellulose steel ammonia solution as a hollowing agent, the average pore diameter is large and the in-plane pore groups are also increased. be able to. In particular, if a coagulant liquid such as the one described above is used as a coagulant instead of only the hollow agent, the above-mentioned characteristics become even more remarkable because coagulation proceeds from both the outer wall and the inner wall of the hollow body.

The following examples will be used to specifically explain the present invention. Examples 1 to 5 Ammonia concentration of cellulose linter (average molecular weight 2.3X] 05) prepared by a known method It was dissolved in a copper ammonia solution having a copper concentration of 6.8% by weight and a copper concentration of 3.1% by weight at various concentrations shown in Table 1, and filtered and defoamed to obtain a spinning stock solution. This spinning dope is transferred to the outer spinning port of the annular spinning port (outer diameter 2 mm).
)Yo? ) At a rate of 2.0 m/min, a mixed solution of water/acetone/ammonia with a ratio of acetone and water of 67.3% by weight and a ratio of ammonia and water of 0.9% by weight was fed into the central spinning spout. (outer diameter 0.41mφ) 2.5 s
At the ratio of I4/win, the ratio of acetone and water is 67.3 by weight, and the ratio of ammonia and water is 0.9.
It was directly discharged into a water/acetone/ammonia mixed solution of 51wt%, then immersed in a 51wt1 sodium sulfide aqueous solution, and then regenerated with 2wt% sulfuric acid at s 5 m/mi.
It was wound up in a water wash bath at a winding speed of n. The moisture in the obtained hollow fibers in a wet state was replaced with acetone, and then air-dried to obtain various conductive porous regenerated cellulose hollow fibers shown in Table 1 (
A film thickness of 23.5 μm was obtained. Copper sulfide was 15% by weight based on the cellulose. <Comparative Example 1> The spinning dope used in Example 3 was fed at a rate of 2.0 il/min from the outer annular spinning opening of the annular spinning opening. On the other hand, a water/methanol-diammonia mixed solution with a ratio of methanol and water of 67.3% by weight and a ratio of ammonia and water of 0.69% by weight was passed through the central spinning outlet at a rate of 2.5114/min, respectively. Discharge directly into a water/methanol/ammonia mixed solution with a methanol to water ratio of 67.3% by weight and an ammonia to water ratio of 0.9% by weight, and then 5% by weight.
It was immersed in a hexasodium sulfur aqueous solution, then regenerated in a 2% by weight sulfuric acid aqueous solution, and wound up in a water washing bath at a winding speed of 5 m/min. The moisture in the resulting wet hollow fibers was replaced with acetone, and then air-dried.

The average pore diameters of the outer and inner wall surfaces of the obtained hollow fibers (film thickness 20 μm) were so small that no pores could be observed with a scanning electron microscope. Therefore, the average pore diameter of the outer and inner wall surfaces is less than 0.02 μm. Also, the surface resistance of the hollow fiber is 185 Q/cIIL, and the water permeability coefficient is 3.6.
x 1O-8(clI4/s@a-al-soaHg
) is 6z.

Below margin

Claims (1)

[Scope of Claims] 1. In the hollow fiber composed of cellulose molecules, the average pore diameter of the inner wall surface and outer wall surface of the hollow fiber is 0.02 to 0.02, respectively.
It is within the range of 1μm, and the in-plane porosity of the outer wall surface is 5
% or more, and has pores penetrating the inner wall surface and the outer wall surface, and copper sulfide or metallic copper is finely dispersed throughout the hollow fiber. 2. In the process of extruding a spinning dope consisting of a cellulose copper ammonia solution through an annular spinning opening, coagulating, regenerating, washing with water, and winding it, the spinning dope is extruded from an outer annular spinning opening and the spinning dope is extruded from a central spinning opening. A conductive material having a hollow portion continuously extending through the entire length of the fiber, which is characterized by discharging liquids exhibiting coagulation properties, causing microphase separation in the fibrous discharge material before coagulation, and subjecting it to sulfurization or reduction treatment after coagulation. A method for producing porous regenerated cellulose hollow fibers. 3. Conductive pore regeneration according to claim 2, in which microphase separation is caused in the spinning dope by directly immersing the discharged fibrous spinning dope in a liquid that exhibits coagulability with respect to the spinning dope. Method for manufacturing cellulose hollow fiber. 4. Both the coagulating liquid discharged from the central discharge port and the coagulating liquid in which the discharged fibrous spinning stock solution is directly immersed do not have hydroxyl groups and have a solubility in a 28% by weight ammonia aqueous solution of 10% by weight or more. The conductive porous regenerated cellulose according to claim 3, which is a mixed solution containing at least one organic solvent that does not swell cellulose and having a composition that causes microphase separation in the cellulose copper ammonia solution. Method for manufacturing hollow fibers. 5. The method for producing conductive porous regenerated cellulose hollow fibers according to any one of claims 2 to 4, wherein the concentration of cellulose in the spinning dope is 4 to 10% by weight. 6. The coagulating liquid discharged from the central discharge hole and the coagulating liquid in which the discharged fibrous spinning stock solution is directly immersed are composed of an organic solvent/ammonia/water system, and the concentration of ammonia relative to water is 5% by weight or less, and The method for producing conductive porous regenerated cellulose hollow fibers according to any one of claims 3 to 5, wherein the concentration of the organic solvent is 20% by weight or more and 160% by weight or less. 7. The method for producing a conductive porous regenerated cellulose hollow fiber according to claim 6, wherein acetone is used as the organic solvent.